This invention relates to expansible shafts and mandrels for supporting rolls and the like, and more particularly, to pneumatically operated expandable bladder shaft structures releasably secured to the core of a roll.
In expandable shafts for supporting rolls, a flexible tube is supported on a rigid tube within a rigid outer cylinder. Radially movable lugs are spaced about the cylinder in openings in the outer cylinder and are radially displaced by expansion of the flexible tube. Pressurized air is supplied to the core of the flexible tube through a journal to expand the tube to radially extend the lugs. The displaced lugs grip the core of a roll in which the expandable shaft is inserted. Such rolls may be large heavy rolls of paper or web material, for example. The shaft provides journals for rotating the supported roll in a process not related to the expandable shaft construction.
The inner rigid tube and outer flexible tube need to be fluid sealed to permit the flexible tube to be expanded in response to the pressurized air. These may form subassemblies which are located within the core of the outer rigid cylinder. U.S. Pat. Nos. 3,391,878; 3,048,345; 3,596,847; 2,331,743; 4,030,415; 4,229,014; 4,461,430; 4,473,195 and 3,908,926 illustrate prior art expansible mandrels or shafts for supporting rolls or the like.
An important criteria recognized by the present inventor is to provide a reliable seal between the inner and outer tubes within the outer cylinder so as to be responsive to pressurized air for expanding the flexible tube. A further criteria recognized is to provide easy access to the inner rigid and flexible tube subassembly for maintenance and repair or replacement as a unit while maintaining the sealed arrangement of the subassembly tubes. A further criteria recognized is to provide easy access to the subassembly while reliably sealing it to the outer cylinder.
In the '878 patent, the flexible tube is sealed by tooth like ridges. These might damage the flexible tube and sacrifice the integrity of the seal. Further, the subassembly is relatively difficult to remove from the outer cylinder because the subassembly is shown staked to one of the journals. Patents '926 and '345 show the flexible tube inserted in mating bores. The '345 patent further shows serrations on a conical plug to effect the sealing. This insertion of the flexible tube into a bore may affect the integrity of the sealing and also add difficulty to axial insertion and removal of the flexible tube due to the relatively high friction between the elements. Patent '743 uses a plurality of sealing membranes and plates which need to be separately assembled and disassembled. For a large number of such membranes this can be tedious. Others of the patents noted above do not address or recognize the problems identified.